autho_explain: Add GUC to log query parameters

auto_explain.log_parameter_max_length is a new GUC part of the
extension, similar to the corresponding core setting, that controls the
inclusion of query parameters in the logged explain output.

More tests are added to check the behavior of this new parameter: when
parameters logged in full (the default of -1), when disabled (value of
0) and when partially truncated (value different than the two others).

Author: Dagfinn Ilmari Mannsåker
Discussion: https://postgr.es/m/87ee09mohb.fsf@wibble.ilmari.org

2 files changed, 23 insertions, 0 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 5d1f7089daf..e29c2ae206f 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -973,6 +973,28 @@ ExplainQueryText(ExplainState *es, QueryDesc *queryDesc)
 }
 
 /*
+ * ExplainQueryParameters -
+ *	  add a "Query Parameters" node that describes the parameters of the query
+ *
+ * The caller should have set up the options fields of *es, as well as
+ * initializing the output buffer es->str.
+ *
+ */
+void
+ExplainQueryParameters(ExplainState *es, ParamListInfo params, int maxlen)
+{
+	char	   *str;
+
+	/* This check is consistent with errdetail_params() */
+	if (params == NULL || params->numParams <= 0 || maxlen == 0)
+		return;
+
+	str = BuildParamLogString(params, NULL, maxlen);
+	if (str && str[0] != '\0')
+		ExplainPropertyText("Query Parameters", str, es);
+}
+
+/*
  * report_triggers -
  *		report execution stats for a single relation's triggers
  */
diff --git a/src/include/commands/explain.h b/src/include/commands/explain.h
index 666977fb1f8..9ebde089aed 100644
--- a/src/include/commands/explain.h
+++ b/src/include/commands/explain.h
@@ -99,6 +99,7 @@ extern void ExplainPrintTriggers(ExplainState *es, QueryDesc *queryDesc);
 extern void ExplainPrintJITSummary(ExplainState *es, QueryDesc *queryDesc);
 
 extern void ExplainQueryText(ExplainState *es, QueryDesc *queryDesc);
+extern void ExplainQueryParameters(ExplainState *es, ParamListInfo params, int maxlen);
 
 extern void ExplainBeginOutput(ExplainState *es);
 extern void ExplainEndOutput(ExplainState *es);